Matrix processor proxy systems and methods

ABSTRACT

In some embodiments, processor-to-processor and/or broadcast proxies are designated in a microprocessor matrix comprising a plurality of mesh-interconnected matrix processors when default processor-to-processor or broadcast routing algorithms used by data switches within the matrix to route messages would not deliver the messages to all intended recipients. The broadcast proxies broadcast messages within individual non-overlapping broadcast domains of the matrix. P-to-P and broadcast proxies may be designated as part of a boot-time testing/initialization sequence. Improving system fault tolerance allows improving semiconductor processing yields, which may be of particular significance in relatively large integrated circuits including large numbers of relatively-complex matrix processors.

RELATED APPLICATION DATA

This application is related to the concurrently-filed U.S. patentapplication Ser. No. 12/168,837, entitled “Matrix ProcessorInitialization Systems and Methods,”, Ser. No. 12/168,853, entitled“Matrix Processor Data Switch Routing Systems and Methods,”, Ser. No.12/168,857, entitled “Matrix Processor Control Message TransmissionSystems and Methods,”, now U.S. Pat. No. 7,870,365 B1, and Ser. No.12/168,861, entitled “Matrix Processor Data Streaming Systems andMethods,”, now U.S. Pat. No. 7,958,341 B1, which are herein incorporatedby reference.

FIELD OF THE INVENTION

This invention relates to digital integrated circuits, and in particularto multi-processor (multi-core) data processing systems and methods.

BACKGROUND OF THE INVENTION

The progress of semiconductor technologies has often outpaced theprogress and evolution of computer architecture. Scaling down the sizeof semiconductor components allows higher logic densities. At the sametime, scaling down the size of semiconductor features introduces newchallenges. Such challenges may involve leakage current, powerconsumption, an inability to increase performance by increasing clockfrequencies, and memory bandwidth capabilities that do not keep up withimproved logic performance. The limitations of current processingsystems are often most apparent in mobile/handheld devices.

SUMMARY OF THE INVENTION

According to one aspect, a method comprises determining whether adefault matrix processor-to-processor routing algorithm would deliver aninter-processor message from a first matrix processor to a second matrixprocessor in a microprocessor matrix of mesh-interconnected matrixprocessors; when the default processor-to-processor routing algorithmwould not deliver the message from the first matrix processor to thesecond processor, determining whether designating a third matrixprocessor as a proxy for the message would cause the message to bedelivered to the second matrix processor; and designating the thirdmatrix processor as a proxy processor for the message when designatingthe third matrix processor as a proxy for the message would cause themessage to be delivered to the second matrix processor.

According to another aspect, an integrated circuit comprises amicroprocessor matrix comprising a plurality of mesh-interconnectedmatrix processors, and a proxy identification unit. Each matrixprocessor comprises a data switch configured to direct inter-processorcommunications within the matrix. The proxy identification unit isconfigured to determine whether a default matrix processor-to-processorrouting algorithm would deliver an inter-processor message from a firstmatrix processor to a second matrix processor; determine whetherdesignating a third matrix processor as a proxy for the message wouldcause the message to be delivered to the second matrix processor whenthe default processor-to-processor routing algorithm would not deliverthe message from the first matrix processor to the second processor; anddesignate the third matrix processor as a proxy processor for themessage when designating the third matrix processor as a proxy for themessage would cause the message to be delivered to the second matrixprocessor.

According to another aspect, a system comprises means for determiningwhether a default matrix processor-to-processor routing algorithm woulddeliver an inter-processor message from a first matrix processor to asecond matrix processor in a microprocessor matrix ofmesh-interconnected matrix processors; means for determining whetherdesignating a third matrix processor as a proxy for the message wouldcause the message to be delivered to the second matrix processor whenthe default processor-to-processor routing algorithm would not deliverthe message from the first matrix processor to the second processor; andmeans for designating the third matrix processor as a proxy processorfor the message when designating the third matrix processor as a proxyfor the message would cause the message to be delivered to the secondmatrix processor.

According to another aspect, a method comprises sending aninter-processor message from a sender matrix processor to a receivermatrix processor through a proxy matrix processor in a microprocessormatrix of mesh-interconnected matrix processors, the message sent by thesender matrix processor designating the proxy matrix processor and thereceiver matrix processor; and employing data switches in each matrixprocessor along a path of the message to route the message from thesender matrix processor to the receiver matrix processor through theproxy matrix processor, wherein a tentative message sent by the sendermatrix processor to the receiver matrix processor through the matrixusing a default processor-to-processor non-proxy data switch routingalgorithm would not reach the receiver matrix processor.

According to another aspect, an integrated circuit comprises amicroprocessor matrix of mesh-interconnected matrix processors, thematrix comprising: a sender matrix processor including a data switchconfigured to send an inter-processor message to a receiver matrixprocessor through the matrix, the message sent by the sender matrixprocessor including a designation of the receiver matrix processor andof a proxy matrix processor through which the message is to be routed; areceiver matrix processor including a data switch configured to receivethe message; and a proxy matrix processor including a data switchconfigured to receive the message from the sender and to send themessage to the receiver. A tentative message sent by the sender matrixprocessor to the receiver matrix processor through the matrix using adefault non-proxy data switch routing algorithm would not reach thereceiver matrix processor.

According to another aspect, a method comprises sending a broadcastmessage from a sender matrix processor in a microprocessor matrix ofmesh-interconnected matrix processors; determining whether a defaultbroadcast algorithm would deliver the broadcast message from the sendermatrix processor to a plurality of receiver matrix processors; and whenthe default broadcast algorithm would not deliver the broadcast messagefrom the sender matrix processor to a subset of the plurality ofreceiver matrix processors, sending processor-to-processor messagescontaining a payload of the broadcast message from the sender matrixprocessor to each of the matrix processors in the subset of theplurality of receiver matrix processors.

According to another aspect, an integrated circuit comprises amicroprocessor matrix of mesh-interconnected matrix processors, thematrix comprising: a plurality of receiver matrix processors; and asender matrix processor including a data switch configured to routeinter-processor messages within the matrix. The sender matrix processoris configured to send a broadcast message within the matrix; and sendprocessor-to-processor messages containing a payload of the broadcastmessage to each of the matrix processors in the subset of the pluralityof receiver matrix processors when the default broadcast algorithm wouldnot deliver the broadcast message from the sender matrix processor to asubset of the plurality of receiver matrix processors.

According to another aspect, a system comprises means for sending abroadcast message from a sender matrix processor in a microprocessormatrix of mesh-interconnected matrix processors; means for determiningwhether a default broadcast algorithm would deliver the broadcastmessage from the sender matrix processor to a plurality of receivermatrix processors; and means for sending processor-to-processor messagescontaining a payload of the broadcast message from the sender matrixprocessor to each matrix processor in a subset of the plurality ofreceiver matrix processors when the default broadcast algorithm wouldnot deliver the broadcast message from the sender matrix processor tothe subset of the plurality of receiver matrix processors.

According to another aspect, a method comprises determining whether adefault broadcast algorithm would deliver a broadcast message from asender matrix processor to a plurality of receiver matrix processors ina microprocessor matrix of mesh-interconnected matrix processors; andwhen the default algorithm would not deliver the message from the sendermatrix processor to a subset of the plurality of receiver matrixprocessors, partitioning the matrix into a plurality of broadcastdomains, and broadcasting the message within each broadcast domain todeliver the message to the subset of the plurality of receiver matrixprocessors.

According to another aspect, an integrated circuit comprises amicroprocessor matrix of mesh-interconnected matrix processors, thematrix comprising a plurality of receiver matrix processors; and asender matrix processor including a data switch configured to routeinter-processor messages within the matrix. The sender matrix processoris configured to send a broadcast message within the matrix configuredas a single broadcast domain when a default broadcast algorithm woulddeliver the broadcast message to the plurality of receiver matrixprocessors; and initiate a sending of the broadcast message within aplurality of broadcast domains when the default broadcast algorithmwould not deliver the broadcast message to a subset of the plurality ofreceiver matrix processors in the matrix configured as single broadcastdomain, wherein sending the broadcast message within the plurality ofbroadcast domains would deliver the broadcast message to the subset ofthe plurality of receiver matrix processors.

According to another aspect, a system comprises means for determiningwhether a default broadcast algorithm would deliver a broadcast messagefrom a sender matrix processor to a plurality of receiver matrixprocessors in a microprocessor matrix of mesh-interconnected matrixprocessors; means for partitioning the matrix into a plurality ofbroadcast domains when the default algorithm would not deliver themessage from the sender matrix processor to a subset of the plurality ofreceiver matrix processors; and means for broadcasting the messagewithin each broadcast domain to deliver the message to the subset of theplurality of receiver matrix processors.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and advantages of the present invention willbecome better understood upon reading the following detailed descriptionand upon reference to the drawings where:

FIG. 1 shows an exemplary data processing system including a processormatrix according to some embodiments of the present invention.

FIG. 2-A shows an exemplary internal structure of a matrix processor ofFIG. 1, according to some embodiments of the present invention.

FIG. 2-B shows an exemplary matrix link numbering for a matrix processorconnected to its neighbors over eight matrix link, according to someembodiments of the present invention.

FIG. 3 shows an exemplary internal structure of a data switch of thematrix processor of FIG. 2-A, according to some embodiments of thepresent invention.

FIG. 4-A shows an exemplary path of a processor-to-processor message ina multi-processor matrix in which all inter-processor links are inworking condition, according to some embodiments of the presentinvention.

FIG. 4-B shows exemplary code describing a processor-to-processormessage routing method according to some embodiments of the presentinvention.

FIG. 5-A shows an exemplary path of a broadcast message in amulti-processor matrix in which all inter-processor links are in workingcondition, according to some embodiments of the present invention.

FIG. 5-B shows exemplary code describing a broadcast message routingmethod according to some embodiments of the present invention.

FIG. 6-A shows an exemplary path of a processor-to-processor message ina multi-processor matrix in the presence of some inter-processorcommunication failures, according to some embodiments of the presentinvention.

FIG. 6-B shows exemplary code describing a fault-tolerantprocessor-to-processor message routing method according to someembodiments of the present invention.

FIG. 7 shows an exemplary failed path of a processor-to-processormessage in the presence of an exemplary configuration of inter-processorcommunication failures, according to some embodiments of the presentinvention.

FIG. 8 shows an exemplary successful path of a processor-to-processormessage through a proxy in the matrix of FIG. 6, according to someembodiments of the present invention.

FIG. 9-A shows an exemplary path of a broadcast message in the presenceof a number of inter-processor communication failures in a single-domainmatrix, according to some embodiments of the present invention.

FIG. 9-B shows an exemplary path of a broadcast message in a matrixcomprising multiple broadcast domains, according to some embodiments ofthe present invention.

FIG. 10-A shows a preliminary boot sequence performed by a bootprocessor according to some embodiments of the present invention.

FIG. 10-B shows an initialization sequence performed by the kernel ofeach matrix processor according to some embodiments of the presentinvention.

FIG. 10-C shows a sequence of steps performed by the kernel of the bootprocessor to identify functional data switches/inter-processor linkswithin the processor matrix, according to some embodiments of thepresent invention.

FIG. 10-D shows a sequence of steps performed by the kernel of the bootmatrix processor to identify functional processing pipelines within theprocessor matrix, according to some embodiments of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The following description illustrates the present invention by way ofexample and not necessarily by way of limitation. Any reference to anelement is understood to refer to at least one element. A set ofelements is understood to include one or more elements. A plurality ofelements includes at least two elements. Unless otherwise specified,each recited element or structure can be formed by or be part of asingle structure or unit, or be formed from multiple distinct structuresor units. Unless otherwise specified, any recited electrical ormechanical connections can be direct connections or indirect operativeconnections established through intermediary circuit elements orstructures. An inter-processor link including non-contentious data andcontrol channels is capable of transferring on the same clock cycle atleast some data messages over the data channel and at least some controlmessages over the control channel without mutual contention; atransmission of at least some control messages over the control channeldoes not directly affect a concurrent transmission of at least some datamessages over the data channel, and vice versa. A data switch configuredto route control messages autonomously with respect to a correspondinginstruction processing pipeline is capable of routing at least somecontrol messages without the execution of corresponding instructions bythe instruction processing pipeline; such a data switch may also becapable of sending control messages in response to execution ofcorresponding instructions by the instruction processing pipeline. Thestatement that two or more events or actions happen synchronously isunderstood to mean that the events/action happen within the same clockcycle. The statement that a data switch transfers two data streamsconcurrently is understood to mean that the transfers of the two datastreams by the data switch overlap temporally, i.e. that at least onsome clock cycles the data switch transfers parts of both data streams;two such streams need not start/end on the same clock cycles.

The following description illustrates embodiments of the invention byway of example and not necessarily by way of limitation.

The systems and methods described below are particularly suited forimplementation using deep sub-micron technologies, where processingelements are small and operate at low power levels. Exemplary systemsand methods as described herein may allow minimizing data movement,which substantially affects system power consumption, performance, andallowable die size characteristics.

FIG. 1 shows an exemplary data processing system 20 according to someembodiments of the present invention. Data processing system 20comprises an integrated circuit 22 including a processor matrix 24.Processor matrix 24 is connected to I/O pin/host interfaces 26 a-b andnorth/south crossbar switches 30 a-b. Crossbar switches 30 a-b connectprocessor matrix 24 to a plurality of memory management units (MMUs) 32a-b, which control the operation of a plurality of memory controllers(MCs) 34 a-b, respectively. Integrated circuit 22 may also include ahost CPU 36, which may be connected to processor matrix 24 through ahost & I/O pin interface 26 a. Host CPU 36 may be a conventionalsingle-core or multi-core processor, such as a processor based on anx86, ARM, MIPS, or SPARC architecture. Interface 26 a may include orotherwise be connected to a boot controller 38. Boot controller 38 mayinclude a boot finite state machine (FSM) for initiating a processormatrix boot sequence described below, as well as a boot read-only memory(ROM) storing data for booting processor matrix 24 and/or host CPU 36.Host CPU 36 may also be connected to a non-volatile memory 40, which mayinclude for example flash memory. Memory controllers 34 a-b areconnected to respective random access memory (RAM) units 44 a-b. Eachmemory controller 34 a-b services a single memory channel, while eachMMU 32 a-b interleaves access to its associated memory channels in orderto increase memory bandwidth utilization. In some embodiments, eachmemory channel may use one or more ranks of memories, each with one ormore DDRx chips.

In some embodiments, system 20 need not include all the components shownin FIG. 1. An exemplary system may include only one of the north/southmemory subsystems shown in FIG. 1, and/or a single memory managementunit. As a further example, a system including a single memorymanagement unit need not include the crossbar switches shown in FIG. 1.

Matrix 24 includes a plurality of mesh-interconnected matrix processors(cores, also denoted below as OVP) 50 arranged in a cartesian (x-y)array configuration. Each matrix processor 50 may be assigned to aspecified subtask of a computationally-intensive application. Theassignment of processors 50 to application tasks may be performed by theapplication and/or load-balancing software known in the art. Theassignment may be performed after a number of testing and initializationsteps described below, which identify any fully- orpartially-non-functional matrix processors 50 (e.g. matrix processors 50having non-functional data switches and/or instruction pipelines,described below).

FIG. 1 shows an exemplary 8×4 matrix configuration, with matrixprocessors 50 denoted by their x- and y-indices. Each matrix processor50 is directly connected through a dedicated data read, data write,control read and control write connection to each of its horizontal,vertical, and diagonal immediate neighbors. Corner matrix processors aredirectly connected to three other matrix processors, non-corner edgematrix processors are directly connected to five other matrixprocessors, and internal matrix processors are directly connected toeight other matrix processors. In the exemplary configuration of FIG. 1,north and south edge matrix processors P0,0-P0,7, P3,0-P3,7 are directlyconnected to north and south crossbar switches 30 a-b, respectively,while west and east edge matrix processors P0,0-P3,0, P0,7-P3,7 aredirectly connected to I/O pin/host interfaces 26 a-b, respectively.

Each matrix processor 50 is connected to one or both of the north andsouth memory subsystems formed by MMUs 32 a-b and MCs 34 a-b. In someembodiments, each matrix processor is connected to the north memorysubsystem including MMUs 32 a and MCs 34 a, and the south memorysubsystem is not present or operative. In some embodiments, each matrixprocessor column is connected to the north memory subsystem over a setof three uni-directional buses including a transaction address, a writedata, and a read data bus.

In some embodiments, some or all matrix processors 50 are programmableprocessors, each including an instruction pipeline configured to executesoftware instructions. In some embodiments, at least some of matrixprocessors 50 may be co-processors. A co-processor may includespecial-purpose hardware (logic) instead of a programmableinstruction-processing pipeline, but otherwise may include theinter-processor communication functions of other matrix processors,described below.

In some embodiments, one or more matrix processors 50 are configured toact as a boot processor to execute a boot/initialization sequence aftereach hard reset and/or other events. For example, the upper-left (0,0)matrix processor 50 may be configured to act as a boot processor bydefault, and the matrix processors 50 in the left column may beconfigured to act as backup boot processors in order of priority goingdown the column if the matrix processor(s) above are not capable offunctioning as boot processors. In addition, one or more matrixprocessors 50 may be designated as a master processor before or afterboot. A master processor may have enhanced privileges and may be capableof selectively performing some operations (e.g. broadcasting messages,domain partitioning, enabling/disabling inter-processor links) that arenot permitted for non-master matrix processors 50. A master processormay be the boot processor, or may be chosen to be a processor near thephysical center of matrix 24 in order to reduce the maximum travel timeof messages from the master matrix processor to other matrix processors50.

Matrix Processor Structure

FIG. 2-A shows an exemplary internal structure of a matrix processor 50according to some embodiments of the present invention. Matrix processor50 includes a hardware data switch 52 controlling inter-processorcommunications as described below, and a programmable instructionprocessing pipeline 54 performing processing operations on incoming dataaccording to a sequence of instructions. Pipeline 54 may include one ormore arithmetic logic units (ALU). Pipeline 54 is connected to dataswitch 52, a register file 58, and an instruction cache (I-cache) 60 a.Data switch 52 is further connected to a local memory 62, a systemcontroller 61, a data cache (D-cache) 60 b, and a direct memory access(DMA) controller 64. Caches 60 a-b, system controller 61 and DMAcontroller 64 are connected to external MMUs through a memory arbiter68. Memory arbiter 68 is connected to MMUs 32 a-b through crossbarswitches 30 a-b and any intervening matrix processors 50; the memoryarbiters of north and south edge matrix processors 50 are directlyconnected to crossbar switches 30 a or 30 b, while the memory arbitersof internal matrix processors 50 are directly connected to the memoryarbiters of their immediate North and South neighbors. In someembodiments, the connections of matrix processors 50 to MMUs 32 a-bthrough memory arbiters 68 generally provide higher latency and lowerbandwidth than the connections to other matrix processors and I/Ointerfaces 26 a-b through data switches 52.

In some embodiments, pipeline 54 and/or the other units connected todata switch 52 in FIG. 2-A may include or be implemented using aconventional processor such as a multi-threaded or single-threadedprocessor based on an x86, ARM, MIPS, or SPARC architecture. In someembodiments, all ports shown in FIG. 2-A are uni-directional full duplexports. Using such ports allows avoiding bus arbitration and switching,and allows achieving higher performance and lower power consumption. Insome embodiments, each port shown in FIG. 2-A includes independentcontrol and data ports, in order to allow matrix processors to exchangecontrol messages without interrupting the streaming of data on the dataports as described below.

In some embodiments, system controller 61 implements one or more systemcontrol functions such as a memory virtualization function. Systemcontroller 61 may include a translation lookaside buffer (TLB) usefulfor improving the speed of virtual address translation and facilitatingmemory virtualization.

In some embodiments, all the ports of data switch 52 are memory mapped;pipeline 54 is capable of writing to such ports directly. Table 1 showsan exemplary division of a 4-Gbyte address space in a system using a32-bit addressing space. Matrix links may be denoted as OVP Links inTable 1 and other tables below.

TABLE 1 Exemplary Matrix Processor Memory Map Address Range Description0x0000_0000-0x7fff_ffff Cached Memory (2 GBytes) 0x8000_0000-0xbfff_ffffLocal Memory (1 GByte) 0xc000_0000-0xc0ff_ffff Direct Memory ControlPort 0 (16 Mbytes) 0xc100_0000-0xc1ff_ffff Direct Memory Control Port 1(16 Mbytes) 0xc200_0000-0xc2ff_ffff Direct Memory Control Port 2 (16Mbytes) 0xc300_0000-0xc3ff_ffff Direct Memory Control Port 3 (16 Mbytes)0xc400_0000-0xc4ff_ffff Local Memory Control Port 0 (16 Mbytes)0xc500_0000-0xc5ff_ffff Local Memory Control Port 1 (16 Mbytes)0xc600_0000-0xc6ff_ffff Local Memory Control Port 2 (16 Mbytes)0xc700_0000-0xc7ff_ffff Local Memory Control Port 3 (16 Mbytes)0xc800_0000-0xc8ff_ffff OVP Control Link 0 (16 Mbytes)0xc900_0000-0xc9ff_ffff OVP Control Link 1 (16 Mbytes)0xca00_0000-0xcaff_ffff OVP Control Link 2 (16 Mbytes)0xcb00_0000-0xcbff_ffff OVP Control Link 3 (16 Mbytes)0xcc00_0000-0xcfff_ffff OVP Control Link 4 (16 Mbytes)0xcd00_0000-0xcdff_ffff OVP Control Link 5 (16 Mbytes)0xce00_0000-0xceff_ffff OVP Control Link 6 (16 Mbytes)0xcf00_0000-0xcfff_ffff OVP Control Link 7 (16 Mbytes)0xd000_0000-0xd0ff_ffff Direct Memory Data Port 0 (16 Mbytes)0xd100_0000-0xd1ff_ffff Direct Memory Data Port 1 (16 Mbytes)0xd200_0000-0xd2ff_ffff Direct Memory Data Port 2 (16 Mbytes)0xd300_0000-0xd3ff_ffff Direct Memory Data Port 3 (16 Mbytes)0xd400_0000-0xd4ff_ffff Local Memory Data Port 0 (16 Mbytes)0xd500_0000-0xd5ff_ffff Local Memory Data Port 1 (16 Mbytes)0xd600_0000-0xd6ff_ffff Local Memory Data Port 2 (16 Mbytes)0xd700_0000-0xd7ff_ffff Local Memory Data Port 3 (16 Mbytes)0xd800_0000-0xd8ff_ffff OVP Link Data Link 0 (16 Mbytes)0xd900_0000-0xd9ff_ffff OVP Link Data Link 1 (16 Mbytes)0xda00_0000-0xdaff_ffff OVP Link Data Link 2 (16 Mbytes)0xdb00_0000-0xdbff_ffff OVP Link Data Link 3 (16 Mbytes)0xdc00_0000-0xdcff_ffff OVP Link Data Link 4 (16 Mbytes)0xdd00_0000-0xddff_ffff OVP Link Data Link 5 (16 Mbytes)0xde00_0000-0xdeff_ffff OVP Link Data Link 6 (16 Mbytes)0xdf00_0000-0xdfff_ffff OVP Link Data Link 7 (16 Mbytes)0xe000_0000-0xefff_ffff System Controller (256 Mbytes)0xf000_0000-0xffff_ffff Boot Memory (256 Mbytes)

FIG. 2-B shows an exemplary relationship between matrix directions andmatrix link indices such as the link indices (0-7) listed of Table 1.The East direction may be defined as Link 0, with the link indexincreasing by one as the direction is changed counterclockwise toNorth-East, North, North-West, West, South-West, South, and South-East.

In some embodiments, the matrix control interfaces are used by theinstruction processing pipeline kernel of each matrix processor 50 toexchange control messages with other matrix processor kernels. In someembodiments, control messages sent by a pipeline 54 of a matrixprocessor 50 are routed by the data switch 52 of that matrix processor mand by data switches of intervening matrix processor(s) 50 en route tothe message destination, without any software involvement or control byany pipelines 54 of intervening matrix processors 50. Kernels of twoimmediately neighboring matrix processors 50 may exchange controlmessages over a control channel at the same time (on the same clockcycle) as user threads in the two processors exchange data over thecorresponding data channel between the processors. In some embodiments,control messages include broadcast messages sent to all processors inmatrix 24, and processor-to-processor (P-to-P) messages sent todesignated recipient processors. Depending on how messages are processedat the destination matrix processor(s) 50, control messages may also beclassified as hardware or software messages. Hardware messages may beused to control low-level functions of matrix 24, such as soft reset andnon-maskable interrupts, boot sequence, clock frequency, and voltagelevel. Software messages may be used to implement message-passingprotocols and inter-processor synchronization, such as support fortransactional memory, thread software interrupts, Compare-And-Swap,Load-Linked and Store-Conditional.

In some embodiments, as long as any two neighboring matrix processors 50use the same clock, data and control messages sent between the twomatrix processors incur only one cycle delay (messages move at one cycleper hop/processor). Double registers may be used on all matrix linkinterfaces, on one side, in order to decouple the timing requirements ofeach data switch 52 from other matrix processors 50. In someembodiments, double registers are used on all inputs, and all outputsare driven combinational. Such a double-register input configurationoffers consistency for the matrix link read interrupts. When a matrixlink read interrupt is set, the last word has just left the source dataswitch 52 and the word is buffered in the destination's input register.

Instruction Pipeline Special-Purpose Registers

In some embodiments, each matrix processor 50 includes a number ofspecial-purpose registers 55 used by pipeline 54 to control theoperation of its corresponding data switch 52. Such registers may behard-coded, or, if software-programmable, writable only by the kernel.In some embodiments, the data switch control special-purpose pipelineregisters include an identification (ID) register, a hardwareconfiguration (HC) register, a software configuration (SC) register, anda port and link (PL) register.

The ID register stores a hard-coded matrix processor ID, which is uniquefor each matrix processor 50 of matrix 24. Table 2 illustrates anexemplary 32-bit ID register according to some embodiments of thepresent invention.

TABLE 2 Identification Register

The Hardware Configuration (HC) register stores hard-coded vertical andhorizontal position indexes identifying the fixed vertical andhorizontal position of matrix processor 50 within matrix 24. Theprocessor positions specified by the HC register are used by routingalgorithms implemented by data switch 52, as described in detail below.Table 3 illustrates an exemplary HC register according to someembodiments of the present invention.

TABLE 3 Hardware Configuration Register

The Software Configuration (SC) register of each matrix processor 50 maystore a programmable index identifying the number (LastV) of activeprocessors in the current column. In some embodiments, the contents ofthe SC register may be written only by the kernel. All matrix processors50 in a column have the same LastV value, but different columns may havedifferent LastV values. In embodiments in which access to the Northmemory subsystem (32 a, 34 a) is daisy-chained for the matrix processors50 in a given column, the number of matrix processors serviced by thecurrent memory arbiter 68 may be used to provide each matrix processor50 equal access to the memory subsystem, independently of verticalprocessor position within the column. If the North memory subsystem isthe only memory subsystem present and one of the matrix processors 50 ina column fails (e.g. is not capable of accessing external memory), thematrix processors below the failed matrix processor in that column nolonger have access to external memory and may be deemed to have alsofailed. Their data switches 52 of such matrix processors may still befunctional and employed for inter-processor communications. Table 4illustrates an exemplary SC register according to some embodiments ofthe present invention.

TABLE 4 Software Configuration Register

In embodiments using a multi-threaded pipeline 54, each port of dataswitch 52 may be allocated for exclusive use by a single thread at atime. The Port and Link (PL) register of each matrix processor 50 maystore a set of memory port and inter-processing link assignment indexes,each indicating a thread to which a corresponding local memory port,direct memory port, or matrix link is assigned. In some embodiments, thecontents of the PL register may be written only by the kernel. Table 5shows en exemplary organization of a Port and Link register for a4-thread pipeline 54.

TABLE 5 Port and Link Register

Data Switch Structure

FIG. 3 shows an exemplary structure of a data switch 52 and its externalconnections according to some embodiments of the present invention. Dataswitch 52 includes matrix routing logic 90 configured to control therouting of matrix messages, pipeline & memory access logic 96 configuredto control pipeline access (input/output) and memory access (read/write,including stream) operations, and testing & initialization logic 98configured to perform a set of testing and initialization stepsdescribed below. In some embodiments, a part of testing & initializationlogic 98 may be present and/or operable only in some matrix processors50, such as the upper left or left-column matrix processors 50. Routinglogic 90 includes broadcast routing logic 92 configured to routebroadcast messages sent to multiple/all matrix processors, andprocessor-to-processor routing logic 94 configured to routeprocessor-to-processor messages having individualized destinations.Pipeline & memory access logic 96 includes logic configured to perform anumber of data streaming operations responsive to the execution ofstream instructions. Data switch 52 further includes a number ofspecial-purpose registers 100.

In some embodiments, each data switch 52 is configured according to aset of configuration parameters set at synthesis time. Suchconfiguration parameters may include the contents of identification (ID)and hardware configuration (HC) special-purpose registers describedabove. Table 6 lists exemplary data switch configuration parameterscorresponding to the ID and HC special-purpose registers describedabove.

TABLE 6 Data Switch Configuration Parameters Parameter Range DescriptionID 0-0xffffffff Matrix Processor Identification V 0-255 VerticalCoordinate in the Matrix H 0-255 Horizontal Coordinate in the Matrix

In some embodiments, each data switch 52 includes a number of interfacesfor connecting to pipeline 54, local memory 62, direct memory controller64, and neighboring matrix processors 50, among others. As shown in FIG.3, data switch 52 may include a pipeline interface 72, an interruptinterface 74, a system controller interface 76, a D-cache interface 78,a local memory interface 80, a direct memory interface 82, a matrixinterface 86, and a boot interface 88. Local memory interface 80includes one or more ports 80 a dedicated to instruction processingpipeline access, and one or more streaming ports 80 b which can be usedto stream data to/from local memory 62.

Data switch pipeline interface 72 includes one or more fields forcommunicating with pipeline 54. Pipeline interface 72 may include aninput command field identifying the data switch access command (e.g.nop, load, store, stream), input data switch address and write datafields, and an output read data field, among others. Input and outputdirections may be defined with respect to data switch 52. Other fieldsmay include an input thread identifier field, as well as outputexception (e.g. link busy) and interrupt fields (e.g. one for eachthread). For example, in some embodiments interrupt signals are sent bydata switch 52 to pipeline 54 when a user thread does a load or storeand the data is not available or cannot be accepted; the requestingthread is preempted to let other threads do useful work while therequesting thread waits, and pipeline 54 is not stalled. When the databecomes available (for loads) or can be accepted (for stores), dataswitch 52 asserts the corresponding interrupt signal for one cycle. Inresponse, pipeline 54 transitions the thread state from a waiting stateto ready. For kernel load and store operations, pipeline 54 may bestalled when the data is not available or cannot be accepted.

In some embodiments, data switch interrupt interface 74 may include oneor more interrupt fields, such as software reset, non-maskable, matrix,memory read (e.g. local memory and direct memory), and matrix link readinterrupts, among others. Data switch system controller interface 76 mayinclude one or more fields for communicating to system controller 61,such as read data, write data, and address fields. Data switch dataD-cache interface 78 may include one or more fields for communicating todata cache 60 b, such as data cache command, data cache virtual address,read data and write data fields.

Local memory pipeline access port 80 a may include one or more fieldsfor allowing pipeline 54 to communicate with local memory 62, such aslocal memory command, local memory address, read data and write datafields. Local memory streaming ports 80 b may include one or more fieldsallowing data streaming to/from local memory 62. For example, in someembodiments local memory streaming ports 80 b may include four streamingwrite and four streaming read ports, with each streaming write portincluding output write data and request-to-send fields and an inputwrite clear-to-send field, and each streaming read port including inputread data and interrupt fields, and input and output flow controlfields. Local memory 62 may include arbitration logic allowing only oneof ports 80 a-b access to local memory 62 on any given clock cycle.Pipeline access port 80 a may be non-blocking, and may have priorityaccess over local memory streaming ports 80 b.

In some embodiments, data switch direct memory interface 82 may includeone or more ports dedicated to instruction processing pipeline access,and one or more streaming ports which can be used to stream data to/fromdirect memory controller 64. A direct memory pipeline-access port mayinclude one or more fields for allowing pipeline 54 to communicate todirect memory controller 64, such as direct memory command, directmemory address, read data and write data fields. Direct memory streamingports may include one or more fields, allowing data streaming to/fromdirect memory controller 64. For example, in some embodiments the directmemory streaming ports may include four streaming write and fourstreaming read ports, with each streaming write port including outputwrite data and write confirmation request fields, and input and outputflow control fields, and each streaming read port including input readdata and interrupt fields, and input and output flow control fields.

In some embodiments, data switch matrix interface 86 may include a datawrite, data read, control write, and control read interface for eachmatrix link (0-7) connected to data switch 52. Each data write andcontrol write interface may include corresponding output write data andinput and output flow control fields, while each data read and controlread interface may include input read data and input and output flowcontrol fields. The data write and data read interfaces may includeoutput data write interrupt and input data read interrupt fields,respectively.

Data switch boot interface 88 may include one or more fields forcommunicating with a boot FSM of boot controller 38. Boot interface 88may include a boot address interface including input boot address andboot address request-to-send fields, and an output boot addressclear-to-send field, and a boot data interface including output bootdata and boot data request-to-send fields and an input boot dataclear-to-send field. In some embodiments, only some data switches 52,for example only the data switches in the left-most matrix processorcolumn, include and/or use boot interface 88.

Data Switch Transactions and Special-Purpose Registers; Data Streaming

In some embodiments, the local memory, inter-processor, and DMAinterfaces of data switch 52 include streaming ports configured tostream data to and from local memory 62, external memory (DMA controller64), immediately neighboring matrix processors 50, andimmediately-neighboring I/O interfaces 26 a-b in response to streaminstructions, described below. Each matrix processor 50 may useload/store instructions to read/write data from/to the streaming portsof its data switch 52, and may also initiate one or more non-blockingdata streams to be transferred in the background by data switch 52without interruption while pipeline 54 continues normal execution overmultiple clock cycles and other data and/or control messages aretransferred over the corresponding data and/or control channels. Theload/store instructions transfer words one at a time (one word perinstruction) between memory-mapped matrix processor ports and processingpipeline registers, while the data streams transfer multiple words overmultiple consecutive clock cycles, one word per cycle, between differentmemory-mapped data switch ports.

In some embodiments, a data stream is initiated by a stream instructionexecuted by pipeline 54. Each stream instruction takes as arguments thesource, destination(s), and size of the data stream. The source may beany one of local memory 62, external memory (DMA controller 64), aneighboring matrix processor 50, or, for processors along the East/Westedges, an I/O interface 26 a-b. The destination(s) may include localmemory 62, external memory (DMA) 64, and/or a neighboring matrixprocessor 50 or I/O interface 26 a-b. In some embodiments, the size ofthe data stream may be fixed by the stream instruction argument, or maybe variable in the case of streams received from neighboring matrixprocessors 50, to be determined by the data source. When the streamsource has sent a last word of a variable-length stream, an interrupt isissued by the stream source, signaling that the stream transmission hascompleted. Variable-length data streams are particularly useful for dataincoming from a neighboring matrix processor. In some embodiments, inorder to improve performance, when a source matrix processor initiates adata stream to one of its immediate neighbors (a destination processor),the destination processor initiates its own data stream from the matrixport connected to the source to a buffer within the destinationprocessor local memory.

Table 7 shows all transactions supported by each data switch 52according to some embodiments of the present invention. As shown in thelast four lines of Table 7, supported data streaming instructionsinclude a data streaming instruction transferring a data stream fromlocal memory to one or more matrix links, a data streaming instructiontransferring a data stream from a matrix link to local memory, a datastreaming instruction transferring a data stream from a matrix link toone or more matrix links, and a data streaming instruction transferringa data stream from a matrix link to local memory and one or more matrixlinks. Data switch 52 includes suitable logic and registers (e.g. streamcontrol/multiplexing logic and stream state registers) configured toimplement each instruction. The fields ds_addr and ds_cmd shown in Table7 may be data switch address and command input fields forming part ofpipeline interface 72. All combinations not shown in Table 7 may betreated as illegal. In some embodiments, the upper 4 KBytes (ds_addr[15:12]==4′hf) of the matrix Link Data Ports can be read and writtenonly by the kernel, and an attempt by a user thread to access this spacecauses an illegal memory transaction exception.

TABLE 7 Data Switch Transactions ds_addr ds_cmd 31:28 27:24 23:16 15:0[3:0] Description 0xxx xxxx 0001, 0010, 0011 Load Byte/Half-Word/Wordfrom DCache 0xxx xxxx 0101, 0110, 0111 Store Byte/Half-Word/Word toDCache 0xxx xxxx 1000 DCache Consistency Synchronization 0xxx xxxx 1010Invalidate DCache Line Unconditionally 0xxx xxxx 1011 Invalidate DCacheLine if Valid 0xxx xxxx 1100 Flush DCache Line 0xxx xxxx 1101 Flush andInvalidate DCache Line 0xxx xxxx 1110 Flush DCache Line and wait cmw_int0xxx xxxx 1111 Flush and Invalidate DCache Line and wait cmw_int 10xxxxxx 0001, 0010, 0011 Load Byte/Half-Word/Word from Local Memory 10xxxxxx 0101, 0110, 0111 Store Byte/Half-Word/Word to Local Memory 110000ss 0011 Load Word from Direct Memory Control Port ss 1100 01ss 0011Load Word from Local Memory Control Port ss 1100 1xxx 0011 Load Wordfrom Data Switch Control 1100 00dd 0111 Store Word to Direct MemoryControl Port dd 1100 01dd 0111 Store Word to Local Memory Control Portdd 1100 1xxx 0111 Store Word to Data Switch Control 1101 00ss 0011 LoadWord from Direct Memory Data Port ss 1101 1sss addr 0011 Load Word fromOVP Link Data sss (1) (ds_addr [15:0] is used only by sourcecoprocessors and I/O blocks) 1101 00dd 0 0111 Store Word to DirectMemory Data Port dd 1101 00dd 4 0111 Store Word to Direct Memory DataPort dd and request a confirmation 1101 10xx mask addr 0111 Store Wordto all OVP Link Data selected by the mask. (1) Send a Read Interrupt tothe Matrix Processor destinations if ds_addr [2] == 1. (ds_addr [15:0]is used only by destination coprocessors and I/O blocks) 1110 xxxx 0011Load Word from System Controller 1110 xxxx 0111 Store Word to SystemController 00ss 00dd 0100 Stream from Direct Memory Data Port ss toDirect Memory Port dd 00ss 01dd 0100 Stream from Direct Memory Data Portss to Local Memory Port dd 01ss 00dd 0100 Stream from Local Memory DataPort ss to Direct Memory Port dd 01ss 01dd 0100 Stream from Local MemoryData Port ss to Local Memory Port dd 01ss 10xx mask addr 0100 Streamfrom Local Memory Data Port ss to OVP Link Data selected by the (1) mask(the addr field is used only by dest. coprocessors and I/O blocks) 1sss01dd addr 0100 Stream from OVP Link Data sss to Local Memory Port dd (1)(the addr field is used only by source coprocessors and I/O blocks) 1sss10xx mask addr 0100 Stream from OVP Link Data sss to OVP Link Dataselected by the mask (the (1) addr field is used only by source anddest. coprocessors and I/O blocks) 1sss 11dd mask addr 0100 Stream fromOVP Link Data sss to Local Memory Port dd and OVP Link (1) Data selectedby the mask (the addr field is used only by source and destinationcoprocessors and I/O blocks)

In some embodiments, when a stream ends or when a store is done with theleast significant bit (LSB) set, the source matrix processor 50 maydrive a link-specific (0,7) data read interrupt signal over a link dataread interface of a matrix link 86, which, if the data stream goes toother matrix processors, in turn may drive a link-specific data writeinterrupt signal over a link data write interface of a matrix link 86and a matrix link read interrupt signal over interrupt interface 74.

In some embodiments, a data switch 52 may simultaneously (on the sameclock cycle) transfer words belong to multiple data streams betweendifferent streaming ports, with the maximum number of data streamshandled simultaneously being limited only by the availability ofstreaming ports. Data switch 52 may include a register for storing adata switch stream state, which is checked every time a streaminstruction is received. Data switch 52 also includes streammultiplexing logic for concurrently (on the same cycle) receiving dataon one streaming port and sending the data on multiple streaming ports.

In some embodiments, thread preemption may occur when a load/store isexecuted from/to D-Cache 60 b, one of the direct memory ports 82 ormatrix links 86. When D-Cache 60 b is involved, D-Cache 60 b may asserta data cache interrupt signal for the corresponding thread over D-cacheinterface 78. For direct memory and matrix links, data switch 52 mayassert a data switch interrupt signal for the corresponding thread overpipeline interface 72.

In some embodiments, a number of resources of each data switch 52 areprogrammable by the kernel, and attempts to write to this address spaceby a user thread cause an Instruction Address Exception. Table 8 shows aset of programmable data switch resources according to some embodimentsof the present invention. Each of the registers listed in Table 8 isdescribed in further detail below.

TABLE 8 Data Switch Address Map Address Description 0xc800_0000 DataSwitch Link Register 0xc800_0004 Data Switch Time-Out Register0xc800_0008 Data Switch Status Register 0xc800_000c Data Switch MessageRead Register (read only) 0xc800_0040-0xc800_007f Data Switch MessageWrite Register (write only)-for I/O messages 0xc810_0000-0xc81f_fffcData Switch Message Write Register (write only)-for Matrix Messages

The data switch link register may be used to enable/disable matrixlinks. Table 9 shows a number of fields of the data switch link registeraccording to some embodiments of the present invention. The fieldsinclude a message-independent link enable field LinkEn specifying whichmatrix links are enabled for all messages, a broadcast link-enable fieldBcstEn specifying which links are enabled for sending broadcastmessages, and a processor-to-processor (P-to-P) link enable field MsgEnspecifying which links are enabled for sending processor-to-processormessages. Each field includes 8 bits, with the value of each bitspecifying a link-enable status (enabled or disabled) for thecorresponding matrix link and/or message type.

TABLE 9 Data Switch Link Register

In some embodiments, the kernel of the boot or master processor candisable matrix links on an individual basis using themessage-independent LinkEn (link enable) bits in the data switch linkregister (see Table 9). This feature may be useful when a neighboringdata switch 52 is defective, or when the boot/master processor kernelwants to partition the processor matrix in several processor domains. Inaddition, the boot/master processor kernel can disableprocessor-to-processor and broadcast message routing through some of theenabled matrix links using the MsgEn and BcstEn bits in the sameregister. When a matrix link has the LinkEn bit set and the MsgEn bitcleared, only processor-to-processor control messages that have theneighbor as a destination will be sent through the link. When a matrixlink has the LinkEn bit set and the BcstEn bit cleared, no broadcastmessages will be sent through the link. These features may be usefulwhen a neighbor has too few enabled matrix links to be useful inprocessor matrix control message routing, when the matrix link isconnected to a coprocessor that does not support the full matrixprocessor link protocol, or the matrix link is connected to an I/Oblock. After a hard- or soft reset, the data switch link register may beset to 0xffffff.

In some embodiments, a number of additional registers may be used tocontrol the operation of each data switch 52. Table 10 through Table 15show a number of such exemplary data switch registers, includingtime-out, status, message read, and message write (forprocessor-to-processor and I/O messages) registers.

TABLE 10 Data Switch Time-Out Register

TABLE 11 Data Switch Status Register

In some embodiments, in the Status register, only the WrBusy, RdBusy,and RdDrop bits are writable, and all other fields are read-only. Insome embodiments, after a hard or soft reset, the Time-Out register isset to 0x00ff, and the WrBusy, RdBusy, and RdDrop bits in the Statusregister are cleared.

TABLE 12 Data Switch Message Read Register

TABLE 13 Data Switch Message Write Register

In some embodiments, each data switch 52 includes two Message registers,a read-only Message Read register and a write-only Message Writeregister. Table 14 shows an exemplary address used to write a matrix(P-to-P or broadcast) message, and Table 15 shows an address used towrite an I/O message to the Message Write register.

TABLE 14 Data Switch Message Write Register Address for Matrix Messages

TABLE 15 Data Switch Message Write Register Address for I/O Messages

In some embodiments, co-processors include fully-functioning dataswitches and are used for routing matrix messages. In some embodiments,co-processors include data switches with limited functionality, used forsending/receiving I/O messages to/from one or more immediatelyneighboring matrix processors 50 but not for routing matrix messagesthrough the co-processor.

Matrix Control Message Streaming: Sending, Receiving

In some embodiments, matrix processors 50 are capable of receiving andsending a set of matrix control messages as described below. The matrixcontrol interfaces of each matrix processor may be used only by thematrix processor kernel to exchange control messages with other matrixprocessor kernels. The matrix control messages may be broadcast orprocessor-to-processor messages. In some embodiments, matrix linkcontrol messages are sent multiplexed on a 17-bit bus (one bit flag and16 bits of data) in two, three, or four consecutive cycles. Each dataswitch 52 is responsible for routing all control messages without anysoftware (pipeline) involvement. Depending on how they are processed atthe destination, the messages may be categorized as hardware andsoftware messages. Hardware messages are processed by the data switchhardware. Software messages are saved in an internal data switchregister and an OVP Matrix Interrupt is set so the messages can beserviced by the kernel. Table 16 shows exemplary fields that are sent onthe matrix link (OVP Link) control interface and Tables 17-20 depict thestructures of four exemplary categories of messages.

TABLE 16 Matrix Link Control Interface Fields

TABLE 17 P-to-P Software Message

TABLE 18 Broadcast Software Message

TABLE 19 P-to-P Hardware Message

TABLE 20 Broadcast Hardware Message

In some embodiments, a bit (e.g. bit 16) of the matrix link controlinterface is used to code the message categories, broadcast/P-to-P andhardware/software. If there are two, three, or four tokens that carrythis bit, there is some redundancy in this bit that can be used todetect some of the tokens in the messages. For example, the last tokenin all messages may have bit 16 cleared. By observing bit 16 in twoconsecutive cycles, a data switch and/or processing pipeline mayconclude the following: a 1 to 0 transition indicates the last twotokens of a message; two consecutive 0s indicate the last token of amessage and the first token of a broadcast message; two consecutive isindicate the source address and the first half of a software message; a0 to 1 transition indicate the source address in the second token.

In some embodiments, the kernel of the boot or master matrix processor50 controls the matrix links of all matrix processors 50 using theLinkEn, MsgEn, and BcstEn bits in the data switch link register (seeTable 9).

In some embodiments, for internal matrix links (links connected toanother matrix processor or a co-processor, all stores to the MessageWrite register using the address described in Table 15 may be considereda nop. When a neighboring data switch 52 is defective, or when theboot/master processor kernel wants to partition the processor matrix inseveral processor domains, the kernel may set the corresponding LinkEnto 0. In this case, no matrix control messages are sent through thecorresponding matrix link.

In some embodiments, if a neighboring matrix processor has too fewenabled matrix links to be useful in matrix control message routing, orwhen the neighbor is a coprocessor that does not support the full matrixlink protocol, the boot/master processor kernel may set thecorresponding LinkEn to 1 and MsgEn to 0; in this case, only matrixcontrol messages that have the neighbor as a destination will be sentthrough it. When the neighbor is a fully functional Matrix Processor,the kernel may set the corresponding LinkEn and MsgEn to 1.

In some embodiments, when a matrix link goes outside matrix 24 (when thelink is connected to an I/O block such as blocks 26 a-b in FIG. 1), allstores to the Message Write register using the address described inTable 14 Table may be considered a nop. When the I/O block is notpresent or defective, the kernel may set the corresponding LinkEn to 0.In this case, no control messages will be sent through the designatedmatrix link. Otherwise, the kernel may set the corresponding LinkEn to1.

In some embodiments, only a matrix processor 50 directly connected to anI/O block (26 a-b) can send control messages to the I/O block, and allsuch messages are point-to-point messages. Such messages may be eitherhardware or software messages. An I/O block may send control messages toany processor within matrix 24. To send messages to internal matrixprocessors 50, an I/O block may use the source address of the matrixprocessor 50 whose matrix link the message is using.

In some embodiments, each matrix processor 50 is capable of receivingmatrix control messages as described below. When any of the control readclear-to-send lines of matrix interface 86 are asserted, the beginningof a matrix link control message is signaled. The messages may beprioritized using a round-robin scheme. If bit 16 of the first token is0, this is a P-to-P message and bits [15:0] contain the coordinates ofthe destination matrix processor 50 and two or three more tokens willfollow with the coordinates of the source matrix processor 50 and themessage itself. If bit 16 of the first token is 1, this is a broadcastmessage and bits [15:0] contain the coordinates of the source matrixprocessor 50 and one or two more tokens will follow with the messageitself.

For P-to-P messages, each data switch 52 may use DstH and DstV todetermine the destination of the message. If (DstH == H && DstV == V),the destination of the message is the current matrix processor 50. Incase of a pre-defined hardware message, data switch 52 may execute themessage, even if the RdBusy flag is set in the Status register. In caseof a software message, data switch 52 may buffer the next two or threetokens (SrcH, SrcV, and Message), and issue an OVP Matrix interrupt. If(DstH !=H ∥ DstV !=V), data switch 52 may forward the message to one ofthe neighboring matrix processors 50. For broadcast messages, dataswitch 52 may buffer and interpret the message, and forward the messageto the neighboring matrix processors.

In some embodiments, when a software message reaches one of itsdestinations, the destination issues an OVP Matrix interrupt oninterrupt interface 74. The message is then available to be read fromthe data switch control space. The Status register (see Table 11Table)identifies the source matrix processor and whether the message is abroadcast or P-to-P message, while the Message Read register (see Table12Table) provides the message. Hardware messages are not written to theMessage Read register. The kernel may clear the OVP Matrix interruptfield in an Interrupt Status register and the RdBusy flag in the DataSwitch Status register before the next message can be accepted. TheRdBusy flag may be cleared by writing a 1 to it, while writing a 0 hasno effect.

In some embodiments, the Time-Out register (see Table 10) specifies themaximum number of cycles an incoming message that has the current matrixprocessor as a destination can be stalled by its data switch 52 in casethe Message Read register is busy (a previous message was received, theOVP Matrix interrupt was issued, and the interrupt was not cleared bythe kernel). If the Message Read register is still busy after thetime-out elapses, the incoming message may be dropped and the RdDropflag may be set in the Status register. This time-out feature may beuseful for avoiding blockages of matrix 24. The RdDrop flag may becleared by writing a 1 to it, while writing a 0 has no effect.

In some embodiments, each matrix processor 50 is capable of sendingmatrix control messages as described below. Each matrix processor 50executes a store to the Message Write register, which automatically setsthe WrBusy flag in the Status register (see Table 11). Data switch 52interprets the stored message, and sends the message starting with thefirst cycle in which no matrix control messages are received. When thelast token leaves data switch 52, the WrBusy flag is cleared and theom_int interrupt is set. If another store to the Message Write registeris executed before the previous message was sent, data switch 52 maystall pipeline 54 until data switch 52 can accept the new message. Thekernel may either wait for the om_int interrupt, or check the WrBusy bitin the Status Register before writing again to the Message Writeregister. To avoid deadlocks, a Real-Time interrupt may be used to set atime-out. The kernel may cancel the message in the Message Writeregister and clear the WrBusy flag in the Status register by writing a 1to it, while writing a 0 has no effect. In some embodiments, the writemessage cancel feature is used only during a reset sequence describedbelow, in which matrix 24 generates a matrix map. The write messagecancel feature is not used after the reset sequence, and the messages inthe processor matrix clear-up after the programmed time-outs in the DataSwitch Time-Out registers.

If a sender matrix processor 50 receives a reply from a destination inresponse to a sent message, a Real-Time interrupt may be used to set atime-out at the sender matrix processor 50, in order to avoid deadlocksin case the message does not reach its destination because of too manyfaulty data switches 52.

In some embodiments, some of the matrix control messages are hardwarematrix control messages, handled in hardware by the receiving matrixprocessor 50. Table 21 shows a set of predefined hardware messagesaccording to some embodiments of the present invention. Message 0 isNull message, i.e. no action is taken by the destination matrixprocessor 50. Message 1 causes a soft-reset in the destination matrixprocessor 50. A soft reset may include setting all internal data switchregisters to their default values and setting a software reset interruptsignal on interrupt interface 74 to HIGH for one cycle, which may causepipeline 54 to set all Special Purpose Registers to their default valuesand execute an unconditional jump to address 0. Message 2 causes anon-maskable interrupt. A non-maskable interrupt may include setting anon-maskable interrupt signal on interrupt interface 74 of thedestination matrix processor 50 to HIGH until the signal is cleared bythe kernel in the Interrupt Status register. Message 3 is used torequest a reply from the destination with the ID register; thedestination data switch 52 responds with a software message with thecontent of the ID register. Messages 4 through 7 are used by otherkernels to write to the Data Switch Control registers; which may beuseful if a matrix processor 50 as a whole is not fully functional (e.g.includes a non-functional pipeline 54), but includes a functional dataswitch 52 which is used to route control messages. Message 8 is used tocontrol the destination matrix processor power supply voltage andmessage 9 to control the clocks. All other hardware messages in Table 21may be reserved for future upgrades.

TABLE 21 Predefined Hardware Messages Message Description 0x0000 NullMessage 0x0001 Software Reset 0x0002 Non-Maskable Interrupt 0x0003 IDregister request 0x0004 Set the Data Switch Link and Time-Out registersto their default values, and clear the WrBusy, RdBusy, and RdDrop bitsin the Data Switch Status register 0x0005 Write the Message to the DataSwitch Time-Out register 0x0006 Write the Message to the leastsignificant half of the Data Switch Link register 0x0007 Write theMessage to the most significant half of the Data Switch Link register0x0008 Control Matrix Processor power supply voltage 0x0009 ControlMatrix Processor clocks 0x000a-0xffff Reserved for future hardwareupgradesDefault Matrix Message Routing

In some embodiments, matrix control messages are routed by data switches52 as described below. Matrix control messages may be routedautomatically by each data switch 52 according to the source position(SrcH, SrcV), current position (CurrH, CurrV) and the destinationposition (DstH, DstV), using the matrix links that are enabled in thedata switch link register (see Table 9). P-to-P messages are interpretedonly by the matrix processor 50 with the H and V coordinates that matchDstH and DstV, and broadcast messages are interpreted by all matrixprocessors 50 except the source matrix processor.

FIG. 4-A shows an exemplary P-to-P message path between a source matrixprocessor having coordinates [4,6] and a destination matrix processorwith coordinates [1,e], according to some embodiments of the presentinvention. FIG. 4-B shows exemplary pseudo-code describing the messagerouting along the path of FIG. 4-A. As shown in FIG. 4-B, if thedestination is reached, an interrupt is issued. To choose a matrix linkfor routing, P-to-P routing logic 94 (FIG. 3) compares the differencesin vertical and horizontal position between the current matrix processorand destination matrix processor. If one difference is more than doublethe other in absolute size, routing logic 94 employs the horizontal orvertical matrix link corresponding to the larger position difference; adiagonal link is chosen otherwise. For example, for the choice ofrouting link by the matrix processor [4,6] for a message withdestination [1,e], the routing logic 94 of the [4,6] matrix processordetermines the difference in horizontal position DeltaH=e−6=8 (indecimal notation, 14−6=8), the difference in vertical positionDeltaV=1−4=−3, and compares the two differences. Routing logic 94 maydetermine the link quadrant to use according to the signs of the twodifferences. If DeltaH>0 and DeltaV<=0, the first (upper right) linkquadrant is chosen. Then, if the absolute value of DeltaH is larger thanthe absolute value of DeltaV, the East link is chosen, i.e. the link tomatrix processor [4,7].

FIG. 5-A shows an exemplary set of paths of a broadcast message sent bya source matrix processor having coordinates [4,6], according to someembodiments of the present invention. The source matrix processor may bea master matrix processor or a selected matrix processor otherwiseenabled to send broadcast messages. FIG. 5-B shows exemplary pseudo-codedescribing the message routing along the paths of FIG. 5-A. The sourceprocessor uses all available links to send the message, as shown for thematrix processor [4,6] in FIG. 5-A. Other processors determine whichlinks to use according to comparisons of the differences in horizontaland vertical positions between the current matrix processor and sourcematrix processor. For example, diagonal links are used if the horizontaland vertical differences are equal (i.e. if the current processor andthe source processor are along a common diagonal line), horizontal linksof the appropriate sign are used if the absolute horizontal differenceis larger than or equal to the absolute vertical difference, andvertical links of the appropriate sign are used if the absolute verticaldifference is larger than or equal to the absolute horizontaldifference.

The exemplary routing methods described with references to FIGS. 4-A-Band 5-A-B may lead to suboptimal results if some of the matrix linksfail. In some embodiments, each data switch 52 implements afault-tolerant routing algorithm that takes advantage of the redundancyof matrix links to route message around failed matrix links.

In some embodiments, matrix 24 includes a number of fault-tolerancecomponents for improving the tolerance of matrix 24 to multiple matrixprocessor failures. The fault-tolerance of matrix 24 is facilitated bythe redundant link structure shown in FIG. 1, which allows messages tobe routed around matrix processors with a failed data switch or that areotherwise incapable of inter-processor communication. Matrix 24 alsoperforms a self-test at power-on to identify which matrix processors 50and matrix links are operational, so that applications make use only offunctional matrix processors 50. At the end of the test, each matrixprocessor 50 knows if any of its neighboring matrix processors 50 ormatrix links are defective. If any matrix processor 50 is notoperational, but its data switch 52 is, all control messages may berouted correctly by the operational data switch 52. If the data switch52 itself is not operational, the neighboring data switches 52 mayre-route all control messages around the defective data switch. Suchfault tolerance features allow using a matrix 24 with multiple failuresfor most applications, and thus allow improving the yield of asemiconductor manufacturing process used to make matrix 24. Such faulttolerance features also provide a self-healing capability after thechips have been deployed in the field.

In some embodiments, a map of functional and failed matrix links 86 andmatrix processors 50 is generated by performing a self-test at power onas described below. Any system application then makes use only offunctional matrix processors 50. At the end of the test, each matrixprocessor 50 will know if any of its immediate neighbor matrixprocessors 50 or matrix links 86 are defective. If any matrix processor50 is not operational, but its data switch 52 is, all control messagescan be routed correctly by the data switch 52. If the data switch 52itself is not operational, the neighboring data switches 52 willre-route all control messages.

In some embodiments, a set of matrix link-enable status indicatorsresulting from the system self-test are used in fault-tolerant P-to-Pand broadcast routing algorithm by each matrix processor 50 as describedbelow. FIG. 6-A shows an exemplary P-to-P message path between a sourcematrix processor having coordinates [4,6] and a destination matrixprocessor with coordinates [1,e] in the presence of some failed matrixprocessors 50 and/or matrix links in between, according to someembodiments of the present invention. FIG. 6-B shows exemplarypseudo-code describing the fault-tolerant message routing along the pathof FIG. 6-A. In FIG. 6-B, use_LinkABCD means that data switch 52 usesLink A if enabled, and if not, Link B, Link C, or Link D in this order.The link numbering is the one shown in FIG. 2-B. As shown, thepseudo-code of FIG. 6-B first selects an ordered list of matrix links(e.g. 0172, 1027, 1203, 2314, 3241, 3425, etc. in FIG. 6-B) according toa set of predetermined inequality relationships between the horizontaland vertical matrix position differences (Delta H, Delta V) between thecurrent and destination matrix processors. From the selected orderedlist, the first (highest-order) enabled link is selected as the matrixlink for routing the message. The matrix link selected to route themessage is the operational link with the direction closest to themessage destination. The message is routed only if it gets closer to thedestination. The message may be dropped otherwise, in order to avoidinfinite loops. As described above, each sender may use a real-timeinterrupt to set a time-out if the sender is waiting for a reply.

Proxy P-to-P Matrix Message Routing

FIG. 7 shows an exemplary P-to-P message path originating at a sourcematrix processor having coordinates [4,6] with a destination of [1,e] inthe presence of a large number of data switch failures, routed accordingto the exemplary pseudo-code of FIG. 6-B. As shown, the routing methoddoes not deliver the message to its destination in the presence of anexcessive number of data switch failures and/or particular failureconfigurations.

In some embodiments, the boot or master processor may designate one ormore proxy matrix processors to be used for forcing the routing ofmessages from given source matrix processors to given destination matrixprocessors through the proxies. A data structure identifying proxies tobe used may be held in external memory or in the local memory of themaster matrix processor.

FIG. 8 shows an exemplary P-to-P message path originating at a source[4,6] with a destination of [1,e], whose routing is forced to occurthrough a proxy [6,8], but otherwise is performed according to thepseudo-code of FIG. 6-B. The message path includes two stages, each ofwhich occurs according to a default routing algorithm such as the oneshown in FIG. 6-B. In the first stage, the message travels from thesource matrix processor ([4,6] in FIG. 8) to the proxy ([6,8] in FIG.8). In some embodiments, each software message to be routed through aproxy may be preceded or followed by a software message including anidentifier of the final (post-proxy) message destination. In the secondstage, after the message arrives at the proxy, the proxy'sinstruction-processing pipeline 54 identifies the message as one to berelayed to a post-proxy destination, identifies the final (post-proxy)destination and sends the message to the post-proxy destination. In someembodiments, more than one intermediate proxy may be used to route amessage between some source-receiver pairs.

FIG. 9-A shows an exemplary set of paths of a broadcast message sent bya source matrix processor having coordinates [4,6] in the presence of anumber of data switch failures, routed according to the exemplarypseudo-code of FIG. 5-B, according to some embodiments of the presentinvention. As shown, the routing method does not deliver the message toall its destinations, and in particular to destination in the shadow ofdefective data switches. Destination not reached by the sent message asshown in dashed lines in FIG. 9-A. In some embodiments, to ensurebroadcast messages are received at all destinations, some messages (e.g.hardware messages) may be sent redundantly on all links, while somemessages (e.g. software messages) may be sent broadcast withinpartitioned domains, as described below.

In some embodiments, broadcast hardware messages (BHM) are used forcritical events. To ensure that such messages reach all matrixprocessors 50 for which a path exists, each data switch 52 may forwardany received BHM on all matrix links except the matrix link on which theBHM was received. Because of the greedy nature of such a fault-tolerantalgorithm, some data switches 52 will receive the same BHM severaltimes. Each data switch 52 may remember a predetermined number of thelatest BHMs in their entirety (Source and Message) and drop allconsecutive identical BHMs. A BHM source does not send two consecutiveidentical BHMs; if a BHM to be sent is identical to animmediately-previous BHM sent by a source, the source may send a NULLBHM first to prevent the sending of two consecutive identical BHMs. Sucha broadcasting algorithm guarantees that all data switches 52 arereached as long as there is a route from source to destination. Becausean island of functional data switches 52 cannot be reached, the sendermay use a real-time interrupt if the sender waits for a reply.

In some embodiments, broadcast software messages (BSM) are used moreoften than BHM; for such messages it may be particularly desirable touse matrix links more efficiently and to avoid the use of NULL messages.In some embodiments, in the absence of defective data switches 52, BSMsmay be routed as described above with reference to FIGS. 5-A-B.

In some embodiments, if matrix 24 includes some defective data switches52 or otherwise inoperative matrix links, a boot matrix processor 50 maydetermine during a system initialization process whether to partitionmatrix 24 in multiple broadcast domains, or to leave matrix 24 as asingle broadcast domain and instead allow the broadcast message sender(e.g. the master matrix processor) to reach any shadowed matrixprocessors 50 by sending individual P-to-P messages to all matrixprocessors 50 in the shadow of defective data switches.

FIG. 9-B shows an exemplary partitioning of matrix 24 into threebroadcast domains; inter-domain boundaries are illustrated by dashedlines in FIG. 9-B. To partition matrix 24, a boot or master matrixprocessor 50 may send P-to-P messages to each matrix processor 50 alongthe domain boundaries to set the BcstEn field in the data switch linkregister to a m value disabling broadcast message transfer through theboundaries. The prospective sender matrix processor 50 (matrix processor(4,6) in FIG. 9-B) selects a domain-specific broadcast proxy (orbroadcast master) for each partitioned domain other than its own (e.g.matrix processors (2,3) and (4,b) in FIG. 9-B), and sends to P-to-Pmessages to each selected proxy for broadcast within each correspondingdomain. The original sender and each selected proxy then broadcasts theBSM within its broadcast domain according to the routing algorithmdescribed with reference to FIGS. 5-A-B. Because an island of functionaldata switches 52 cannot be reached, each broadcast sender may use areal-time interrupt if the sender waits for a reply.

Boot/Reset/Initialization; Matrix Functionality Map, P-to-P andBroadcast Proxy Assignment

In some embodiments, matrix 24 performs a number of initialization andtesting steps upon hard and/or soft resets, as described below. Some orall of the testing/initialization steps described below may also beperformed at periodic time intervals, for example once a day or after apredetermined number of hours has elapsed from the latest test.Information resulting from the testing/initialization is stored and usedat two levels, locally and globally. Local information may be used inhardware-directed matrix message routing, and global information insoftware-directed decisions on assignments of matrix processors toapplication function, P-to-P proxy assignment, and broadcast domainpartitioning and broadcast proxy assignment. Locally, each data switch52 stores information about its matrix link functionality statusindicators (message-independent enabled, broadcast-enabled, and/orP-to-P enabled) in its link status hardware, which is used for routingmatrix messages. Globally, a matrix functionality map is stored in thelocal memory of the master matrix processor 50 and/or in externalmemory. At least parts of the matrix functionality map may be used toset local matrix link functionality status indicators. In someembodiments, a boot matrix processor 50 acts as a matrix mapping andproxy assignment unit, directing the generation of the matrixfunctionality map as described below; matrix 24 may be then thought tobe formed by all matrix processors 50 outside of the boot matrixprocessor. In some embodiments, dedicated mapping and/or proxyassignment units/processors linked to matrix 24 may be providedseparately from any matrix processor 50.

After a hard-reset, all matrix processors 50 are in a boot state. In theboot state, all m user threads are in an idle state and the kernel ofeach matrix processor 50 is active. The matrix processors 50 in thefirst column (e.g. left-most column) start fetching instructions fromthe boot/reset address segment (see Table 1). The I-cache 60 a (FIG.2-A) of each matrix processor in the first column forwards theinstruction fetching request to data switch 52, which assigns therequests to matrix data link 4 (West). The incoming data received inresponse to a each request is stored by I-cache 60 a and executed bypipeline 54. The matrix processors 50 not in the first column stay inthe boot state until receiving a Software Reset message.

In some embodiments, one of the matrix processors 50 in the first columnis selected by a boot finite state machine (FSM) as a boot controlprocessor. The boot FSM may form part of boot controller 38 (FIG. 2-A).For example, the top left (0,0) processor may be selected if functional.If the top left processor does not respond on matrix link 4 (West) withan interrupt after a predetermined number of cycles, the next processor(1,0) is selected and tested, and so on.

In some embodiments, the selected boot matrix processor 50 performs aboot sequence comprising a number of steps shown in FIG. 10-A. In a step180, the selected boot matrix processor 50 performs a minimal chipinitialization and self-test. In a step 182, the boot matrix processor50 performs a store to a predetermined address corresponding to matrixlink 4 (West) with destination Read Interrupt (e.g. address0xd810_(—)0004) to confirm that the selected boot matrix processor 50 isfunctional. In a step 186, the current application program and data arecopied from NVM 40 (FIG. 1) to RAM 44 a-b. In a step 188, the bootmatrix processor 50 broadcasts a Control Message 0 (Software Reset) toreset all other matrix processors 50 in matrix 24. In a step 190, theboot code performs a jump to the Soft Reset handler (address 0), whichis in the cacheable address space. The boot matrix processor 50 thentransitions from the boot state to the normal execution state (step192).

In some embodiments, after a hard-reset and before any applicationstarts, each matrix processor 50 programs the Data Switch Link andTime-Out registers (see Tables 8-10), and the boot matrix processor 50sends software messages to all other matrix processors to ensure aconsistent configuration of all matrix processors 50 in matrix 24.

In some embodiments, after each software reset, the kernel of eachmatrix processor 50 may go through the steps shown in FIG. 10-B toidentify which matrix links are functional and thus generate a matrixlink functionality map. In a step 200, a P-to-P ID register requestmessage is sent to each immediate neighbor over the corresponding matrixlink. A time out is then set (step 202). The time-out may be set using areal-time interrupt or polling, and is sufficient to allow the immediateneighbors time to respond. For example, the time-out period may bechosen to be on the order of a few hundred clock cycles. Each kernelthen waits to receive matrix (OVP) interrupts from the immediateneighbors (step 204), and the contents of the data switch link register(see Table 9) are set according to the received responses (step 206). Ifan immediate neighbor does not respond, the corresponding link isdisabled using the LinkEn field of the data switch link register. If animmediate neighbor responds, the corresponding link is enabled using thesame field.

In some embodiments, after the first broadcast Software Reset sent bythe boot matrix processor 50, the kernel of the boot matrix processor 50performs the steps of FIG. 10-B, and subsequently the sequence of stepsshown in FIG. 10-C. In a step 220, a time out is set. The time-out maybe set using a real-time interrupt or polling. The time-out period maybe chosen to be on the order of a few thousand clock cycles. In a step224, a broadcast ID register request message is sent to all matrixprocessors 50. A time-out sufficient to receive ID request responses(e.g. on the order of a few thousand clock cycles) is set using areal-time interrupt or polling (step 226). In some embodiments, P-to-Pbroadcast ID register request messages may be sent to all matrixprocessors 50 instead of a broadcast ID register request. The bootprocessor kernel waits to receive interrupts from matrix processors 50(step 228), and subsequently builds a matrix map of functioning dataswitches and/or matrix links according to the received responses (step230). The matrix map may include a data structure identifying the matrixpositions of each functional and non-functional data switch 52. In astep 234, the boot processor kernel determines how each functioning dataswitch 52 can be reached, and generates a map of functional matrixlinks. In a step 236, the boot matrix processor kernel programs thespecial-purpose registers (described above) of all functioning dataswitches 52 using hardware control messages. The message independentlink-enable field values (see Table 9) of the link status register areset to an enabled or disabled status according to the matrix linkfunctionality map. In a step 238, the kernel may program at least somepipeline internal special purpose registers. After the sequence of stepsof FIG. 10-C has been performed, the hardware of the boot matrixprocessor 50 and all directly reachable data switches 52 areinitialized, and the topology of matrix 24 has been determined.

In some embodiments, the kernel of the boot matrix processor 50subsequently performs a sequence of steps, shown in FIG. 10-D, todetermine which matrix processors 50 include functional processorpipelines 54 and other processor components shown in FIG. 2-A, and notmerely functional data switches 52, and to select P-to-P and/orbroadcast proxies if needed. In a step 240, the kernel sends softwarecontrol messages to all matrix processors 50 previously determined tohave functional data switches 52. The software control messages requestthe recipient matrix processors 50 to perform a hardware self-test andreport test result indicators/status to the boot matrix processorkernel. The self-test includes checking whether each matrix processor 50can access (read/write to/from) external memory and local memory. In astep 242, the kernel sets a real-time interrupt or polling time-outsufficient to allow the self-tests and reporting to be performed. Thekernel waits to receive interrupts from matrix processors 50 (step 244),and subsequently builds a matrix map of functioning matrix processors 50according to the received responses (step 246). The matrix map mayinclude a data structure identifying the matrix positions of eachfully-functional and non-functional matrix processor 50.

In a step 248, one or more proxies are selected if needed to ensureadequate communication between matrix processors 50 in the presence ofdata switch failures. A proxy selection process may be startedselectively only if it is possible that there are functioning dataswitches 52 whose ID messages could not reach the boot matrix processor50. The proxy selection process may include a P-to-P proxy selectionstep and a broadcast proxy selection step.

In some embodiments, to identify a P-to-P proxy, the boot matrixprocessor kernel first determines whether a default (non-proxy) P-to-Prouting algorithm (e.g. a routing algorithm such as the ones illustratedin FIGS. 4-A-B, 6-A-B and 7) will deliver messages from all sendermatrix processors to all receiver matrix processors having functioningdata switches. Such a determination may simulate message routingselectively in matrix regions having concentrated data switch/matrixlink failures, for example a fraction of failed matrix links thatexceeds a predetermined threshold in any matrix region (e.g. square) ofpredetermined size. When the default (non-proxy) routing algorithm wouldnot succeed in delivering a message from a given sender to a givenreceiver, one or more proxy candidates may be evaluated to determinewhether designating the candidate as a proxy would ensure delivery ofthe message from the sender to the receiver. The message would travel ineach of its two stages (sender-proxy and proxy-receiver) according tothe default routing algorithm, and each matrix processor along themessage path would perform its routing decision according to the defaultrouting algorithm. The proxy candidates may be chosen to be proximal tothe edges of regions with relatively high densities of failed matrixlinks/data switches. If designating a proxy candidate as a proxy wouldcause P-to-P messages to be delivered from the sender to the receiver,the proxy candidate is designated as a proxy for the givensender/receiver pair. The identity of the selected proxy may beremembered and used as a proxy candidate for subsequent evaluations ofdifferent sender/receiver pairs. If a single proxy candidate is notfound, the total message path may be divided into three segmentscorresponding to two sequential proxies between the source anddestination. Higher numbers of proxies may be used if two proxies arenot sufficient. Each proxy may be treated as a new destination, and aproxy identification process may be performed as described above forsegments of the original source-destination path.

In some embodiments, to identify a broadcast proxy and correspondingbroadcast domain boundaries, the boot matrix processor first determineswhether a default (single-domain) broadcast routing algorithm (e.g. arouting algorithm such as the one illustrated in FIGS. 5-A-B and 9-A)will deliver a broadcast message from a broadcast sender (e.g. aprospective master matrix processor 50) to all other matrix processors50 having functioning data switches. When the default broadcast routingalgorithm would not succeed in delivering the broadcast message to atleast some receivers, the boot processor kernel may determine whether topartition matrix 24 in multiple broadcast domains, or to leave matrix 24as a single broadcast domain and instead allow the broadcast messagesender (e.g. the master matrix processor) to reach any shadowed matrixprocessors 50 by sending individual P-to-P messages to all matrixprocessors 50 in the shadow of defective data switches. The bootprocessor kernel may first determine how many matrix processors wouldnot be reached by a single-domain (default) broadcast message routingalgorithm, and may determine one or more broadcast domain partitionboundaries and broadcast proxy positions suitable for reaching theshadowed matrix processors 50. Tentative domain partition boundaries maybe chosen to abut non-functioning data switches, while tentativebroadcast proxy locations may be chosen to be generally centered withintheir corresponding domains. P-to-P message delivery may be chosen forexample when the number of shadowed matrix processors meets apredetermined threshold condition (e.g. is less than 4 or 8), or if adomain partitioning able to reach the shadowed processors is not readilyfound using a number of broadcast domains meeting a predeterminedthreshold condition (e.g. less than 4 or 8 domains). Broadcast domainpartitioning may be chosen for example when the number of shadowedmatrix processors meets a predetermined threshold condition (e.g. ishigher than or equal to 4 or 8), and a domain partitioning able to reachthe shadowed processors is readily found using a number of broadcastdomains meeting a predetermined threshold condition (e.g. less than orequal to 4 or 8 domains). Matrix 24 may be partitioned in multiplebroadcast domains using the BcstEn field in the data switch linkregister (Table 9) of each data switch 52 along the domain boundaries.

If any P-to-P and/or broadcast proxies are selected, the sequences ofsteps shown in FIGS. 10-C and 10-D are repeated to identify which dataswitches 52 and matrix processors 50 are functional and reachablethrough the selected proxies (step 250). When the matrix mapping processhas converged, matrix processors 50 are sent control messages withinternal special-purpose register values for each matrix processor 50(step 254). Following the above steps, the topology of matrix 24 hasbeen determined and all hardware has been initialized. In a step 256,the boot matrix processor 50 (e.g. the top left processor) hands overcontrol to a master matrix processor 50 (e.g. a centrally-locatedprocessor such as the [4,6] processor). The control handover may includetransferring the data structure (or a pointer to the data structure)representing the data switch and/or matrix processor functionality mapto the master matrix processor 50. In a step 260, the kernel of themaster matrix processor 50 performs a software specific initializationand launches the application of interest.

In some embodiments, matrix 24 may include a number of power-savingfeatures. Matrix 24 may use two levels of clock gating. A high level maybe controlled by the link control messages 8 and 9 listed in Table 21),and a low level may be controlled by the hardware for each individualregister; a register clock is enabled only when the register contentneeds to change. In addition, each matrix column may use a differentclock and Vdd voltage. If different clocks and/or Vdd voltages are usedin different columns, the matrix links between matrix columns withdifferent clocks may include synchronization registers in order to avoidmeta-stability. Moreover, in some embodiments some of the matrix columns(e.g. a number of columns on the right side of matrix 24 in FIG. 1) canbe selectively shut down completely. Similarly, some individual matrixprocessors 50 (e.g. a number of bottom matrix processors 50 inparticular columns) can be selectively shut down completely. When anumber of matrix processors 50 at the bottom of a column are shut down,the LastV field in the software configuration register (see Table 4) ofthe remaining active matrix processors 50 in the column may be set tothe last active matrix processor 50 in the column.

In some embodiments, some of the matrix processors 50 include dedicatedprocessing hardware rather than programmable pipelines 54. Such unitsmay be used to implement functions for which high performance isparticularly useful at low power levels. Such processing logic mayimplement mostly data path functions, and the hardware required may berelatively small and easy to design and verify. Such matrix processors50 may include a data switch 52 and memory arbiter 68 (FIG. 2-A) asdescribed above, and may behave on their external interfaces in the sameway as programmable matrix nodes. For example, all link control messagesmay be routed identically in such matrix nodes as in programmable matrixnodes.

Exemplary systems and methods as described above allow addressing anumber of limitations of conventional computer systems. Such limitationsare of particular relevance for mobile devices, which incorporateincreasingly complex functionality but are subject to stringent powerconstraints. Such limitations can be addressed by changes to bothconventional hardware and software approaches. Exemplary systems andmethods as described above allow employing a new hardware architecturethat uses aspects of the serial algorithmic thinking that has beenadopted by generations of software engineers and is thus difficult tochange rapidly.

The evolution of semiconductor technology through scaling of featuresizes and transistor counts brings both benefits and challenges. Amongthe benefits is higher logic density. As logic gates are relativelyinexpensive in terms of silicon area, complex functionality that wasunthinkable until a few years ago is becoming commercially viable. Atthe same time, although the price per chip may go down, the tape-outcost has often gone up significantly, as have the development costs ofcomplex SOCs (System-On-Chip). Other challenges include leakage currentand power consumption in general, the ineffectiveness of attempts toincrease performance by increasing clock frequency, and the commoninability of memory bandwidth to keep up with increased logicperformance. These limitations have led to the current developments inthe areas of parallel processing, multicore, and mixed cores.

Multi-core systems face a different set of challenges, which are oftenrelated to inter-processor communications. Exemplary systems and methodsas described above allow improved inter-processor communications,particularly in the presence of errors that disable at least some matrixprocessors and/or data switches. The exemplary fault tolerance aspectsdescribed above allow improvements in manufacturing yields as well asimproved tolerance to failures in the field.

The above embodiments may be altered in many ways without departing fromthe scope of the invention. For example, a matrix may be a 3-D matrixincluding multiple stacked 2-D matrix layers, with matrix processorsinterconnected in-plane and along the stacking direction. Accordingly,the scope of the invention should be determined by the following claimsand their legal equivalents.

1. A method comprising: determining whether a default matrixprocessor-to-processor routing algorithm would deliver aninter-processor message from a first matrix processor to a second matrixprocessor in a chip comprising a microprocessor matrix ofmesh-interconnected matrix processors, wherein the message routedaccording to the default matrix processor-to-processor routing algorithmwould be routed from the first matrix processor by a data switch in eachmatrix processor along a default message path originating at the firstmatrix processor; in response to determining whether the default matrixprocessor-to-processor routing algorithm would deliver the message fromthe first matrix processor to the second matrix processor, when thedefault processor-to-processor routing algorithm would not deliver themessage from the first matrix processor to the second processor,determining whether designating a third matrix processor as a proxy forthe message would cause the message to be delivered to the second matrixprocessor using the default matrix processor-to-processor routingalgorithm from the first matrix processor to the third matrix processorand subsequently from the third matrix processor to the second matrixprocessor, wherein the third matrix processor is not in the defaultmessage path; and in response to determining whether designating thethird matrix processor as a proxy for the message would cause themessage to be delivered to the second matrix processor, designating thethird matrix processor as a proxy for the message when designating thethird matrix processor as a proxy for the message would cause themessage to be delivered to the second matrix processor; wherein thedefault matrix processor-to-processor routing algorithm determines amessage propagation direction at a current matrix processor according toa comparison between a first quantity and a second quantity, wherein thefirst quantity is a difference between vertical position indexes of thecurrent matrix processor and a destination matrix processor, and whereinthe second quantity is a difference between horizontal position indexesof the current matrix processor and the destination matrix processor. 2.The method of claim 1, further comprising routing the message throughthe proxy processor to deliver the message to the second matrixprocessor.
 3. The method of claim 1, wherein designating the thirdmatrix processor as a proxy processor is performed by a boot matrixprocessor configured to perform a matrix boot sequence.
 4. The method ofclaim 1, comprising determining whether the defaultprocessor-to-processor routing algorithm would deliver theinter-processor message from the first matrix processor to the secondmatrix processor upon each hard reset of the microprocessor matrix. 5.The method of claim 1, wherein determining whether the default matrixprocessor-to-processor routing algorithm would deliver theinter-processor message from the first matrix processor to the secondmatrix processor is performed according to a matrix functionality mapdesignating a functional or non-functional status for eachinter-processor link in the microprocessor matrix.
 6. An integratedcircuit comprising: a microprocessor matrix comprising a plurality ofmesh-interconnected matrix processors integrated on a chip, wherein eachmatrix processor comprises a data switch configured to directinter-processor communications within the matrix; and a proxyidentification unit configured to determine whether a default matrixprocessor-to-processor routing algorithm would deliver aninter-processor message from a first matrix processor to a second matrixprocessor, the message being routed according to the default matrixprocessor-to-processor routing algorithm along a default message pathoriginating at the first matrix processor; in response to determiningwhether the default matrix processor-to-processor routing algorithmwould deliver the message from the first matrix processor to the secondmatrix processor, when the default processor-to-processor routingalgorithm would not deliver the message from the first matrix processorto the second processor, determine whether designating a third matrixprocessor as a proxy for the message would cause the message to bedelivered to the second matrix processor using the default matrixprocessor-to-processor algorithm from the first matrix processor to thethird matrix processor and subsequently from the third matrix processorto the second matrix processor, wherein the third matrix processor isnot in the default message path; and in response to determining whetherdesignating the third matrix processor as a proxy for the message wouldcause the message to be delivered to the second matrix processor,designate the third matrix processor as a proxy for the message whendesignating the third matrix processor as a proxy for the message wouldcause the message to be delivered to the second matrix processor;wherein the default matrix processor-to-processor routing algorithmdetermines a message propagation direction at a current matrix processoraccording to a comparison between a first quantity and a secondquantity, wherein the first quantity is a difference between verticalposition indexes of the current matrix processor and a destinationmatrix processor, and wherein the second quantity is a differencebetween horizontal position indexes of the current matrix processor andthe destination matrix processor.
 7. The integrated circuit of claim 6,wherein the proxy identification unit comprises at least part of a bootmatrix processor configured to perform a matrix boot sequence.
 8. Theintegrated circuit of claim 6, wherein the proxy identification unit isconfigured to determine whether the default processor-to-processorrouting algorithm would deliver the inter-processor message from thefirst matrix processor to the second matrix processor upon each hardreset of the microprocessor matrix.
 9. The integrated circuit of claim6, wherein determining whether the default matrix processor-to-processorrouting algorithm would deliver the inter-processor message from thefirst matrix processor to the second matrix processor is performedaccording to a matrix functionality map designating a functional ornon-functional status for each inter-processor link in themicroprocessor matrix.
 10. A system comprising: means for determiningwhether a default matrix processor-to-processor routing algorithm woulddeliver an inter-processor message from a first matrix processor to asecond matrix processor in a chip comprising a microprocessor matrix ofmesh-interconnected matrix processors, wherein the message routedaccording to the default matrix processor-to-processor routing algorithmwould be routed from the first matrix processor by a data switch in eachmatrix processor along a default message path originating at the firstmatrix processor; means, responsive to the means for determining whetherthe default matrix processor-to-processor routing algorithm woulddeliver the message from the first matrix processor to the second matrixprocessor, for determining whether designating a third matrix processoras a proxy for the message would cause the message to be delivered tothe second matrix processor using the default matrixprocessor-to-processor routing algorithm from the first matrix processorto the third matrix processor and subsequently from the third matrixprocessor to the second matrix processor, wherein the third matrixprocessor is not in the default message path; and means, responsive tothe means for determining whether designating the third matrix processoras a proxy, for designating the third matrix processor as a proxy forthe message when designating the third matrix processor as a proxy forthe message would cause the message to be delivered to the second matrixprocessor; wherein the default matrix processor-to-processor routingalgorithm determines a message propagation direction at a current matrixprocessor according to a comparison between a first quantity and asecond quantity, wherein the first quantity is a difference betweenvertical position indexes of the current matrix processor and adestination matrix processor, and wherein the second quantity is adifference between horizontal position indexes of the current matrixprocessor and the destination matrix processor.